Some nozzle devices may comprise a piezoelectric actuator which transforms electrical energy to mechanical energy in the form of high frequency waves, such as megasonic waves of acoustic vibrational frequencies in the mega-hertz range. Megasonic waves are highly focused in nature. This vibrational energy actuates a working fluid to enhance the energy of the working fluid which when directed at a working surface by a nozzle increases the effectiveness of the working fluid for cooling, cleaning and/or lubricating the working surface.
For example, when nozzle devices energized by megasonic waves are applied in precision machining, the machining performance is improved when the energized working fluid reaches the proximity of a cutting point. As a result, this increases the cooling and lubricating performance of the working fluid.
In another application, such nozzle devices are useful for cleaning semiconductor devices which must be thoroughly cleaned to remove microscopic debris before subjecting them to downstream fabrication processes. Contaminant particles of sizes in the submicron range can be removed from the surface of a semiconductor device when a drag force is exerted on the contaminant particles causing these particles to oscillate.
A conventional nozzle device 100 is illustrated in FIG. 1, which comprises a piezoelectric actuator 102 located at the rear of the device 100 along a principal axis P of the device 100. High frequency waves such as megasonic or ultrasonic waves 120 may be generated by the piezoelectric actuator 102 along the principal axis P towards a fluid outlet 108. A working fluid supply provides a working fluid 104 into a nozzle chamber 118 of the device 100 through a fluid inlet 106 at a side of the device 100 in a direction perpendicular to the principal axis P. The working fluid 104 crosses the path of the waves 120 at an angle and absorbs the vibrational energy transmitted by the waves 120. The energy in the working fluid 104 is thus enhanced and the working fluid 104 is now energized to form an actuated working fluid 110 which changes its direction of movement 116 in the nozzle chamber 118 before being discharged through the fluid outlet 108 of the nozzle chamber 118.
Examples of prior art cleaning nozzles which utilize the principles of the aforesaid conventional nozzle device 100 are Japanese Publication Number JP2003340330 (A) entitled “Ultrasonic Cleaning Nozzle, Apparatus Thereof and Semiconductor Device” and U.S. Pat. No. 5,927,306 entitled “Ultrasonic Vibrator, Ultrasonic Cleaning Nozzle, Ultrasonic Cleaning Device, Substrate Cleaning Device, Substrate Cleaning Treatment System And Ultrasonic Cleaning Nozzle Manufacturing Method”. In both of these publications, ultrasonic cleaning nozzles are disclosed in which cleaning fluid enters a nozzle chamber at right angles to the direction of propagation of an ultrasonic wave.
However, there are shortcomings in such conventional ultrasonic or megasonic nozzle devices 100. As the working fluid 104 is introduced into the nozzle device 100 in a direction perpendicular to the direction of propagation of the high frequency waves 120, the waves 120 are distorted by the flow of the working fluid 104. A significant amount of vibrational energy of the high frequency waves 120 is lost as a result, which reduces the vibrational energy transmitted from the waves 120 to the working fluid 104. This decreases the cleaning and cooling effect of the nozzle device 100.
Furthermore, there is a sudden directional change of the working fluid 104 at a wave generation side 112 of the piezoelectric actuator 102. This creates a turbulent flow 114 which introduces an air barrier between the piezoelectric actuator 102 and the working fluid 104. Therefore, the efficiency of transmission of vibrational energy from the high frequency waves 120 to the working fluid 104 decreases. The turbulent flow 114 also affects the communication between the piezoelectric actuator 102 and the working fluid 104 which impedes the propagation of the waves 120 through the working fluid 104. The working fluid 104 is also less efficient in carrying away the heat generated by the piezoelectric actuator 102 due to the turbulent flow 114. Hence, excessive heat generated by the piezoelectric actuator 102 may shorten the lifespan of the piezoelectric actuator 102.
It would be desirable to increase the working efficiency of a nozzle device for cooling, cleaning and/or lubricating during machining by aligning the flow of the working fluid 104 with the direction of propagation of the high frequency waves 120.